FGF-2b and h-PL Transform Duct and Non-Endocrine Human Pancreatic Cells into Endocrine Insulin Secreting Cells by Modulating Differentiating Genes.

Background: Diabetes mellitus (DM) is a multifactorial disease orphan of a cure. Regenerative medicine has been proposed as novel strategy for DM therapy. Human fibroblast growth factor (FGF)-2b controls ß-cell clusters via autocrine action, and human placental lactogen (hPL)-A increases functional ß-cells. We hypothesized whether FGF-2b/hPL-A treatment induces ß-cell differentiation from ductal/non-endocrine precursor(s) by modulating specific genes expression. Methods: Human pancreatic ductal-cells (PANC-1) and non-endocrine pancreatic cells were treated with FGF-2b plus hPL-A at 500 ng/mL. Cytofluorimetry and Immunofluorescence have been performed to detect expression of endocrine, ductal and acinar markers. Bromodeoxyuridine incorporation and annexin-V quantified cells proliferation and apoptosis. Insulin secretion was assessed by RIA kit, and electron microscopy analyzed islet-like clusters. Results: Increase in PANC-1 duct cells de-differentiation into islet-like aggregates was observed after FGF-2b/hPL-A treatment showing ultrastructure typical of islets-aggregates. These clusters, after stimulation with FGF-2b/hPL-A, had significant (p < 0.05) increase in insulin, C-peptide, pancreatic and duodenal homeobox 1 (PDX-1), Nkx2.2, Nkx6.1, somatostatin, glucagon, and glucose transporter 2 (Glut-2), compared with control cells. Markers of PANC-1 (Cytokeratin-19, MUC-1, CA19-9) were decreased (p < 0.05). These aggregates after treatment with FGF-2b/hPL-A significantly reduced levels of apoptosis. Conclusions: FGF-2b and hPL-A are promising candidates for regenerative therapy in DM by inducing de-differentiation of stem cells modulating pivotal endocrine genes.

Nova1 is a master regulator of alternative splicing in pancreatic beta cells.

Alternative splicing (AS) is a fundamental mechanism for the regulation of gene expression. It affects more than 90% of human genes but its role in the regulation of pancreatic beta cells, the producers of insulin, remains unknown. Our recently published data indicated that the 'neuron-specific' Nova1 splicing factor is expressed in pancreatic beta cells. We have presently coupled specific knockdown (KD) of Nova1 with RNA-sequencing to determine all splice variants and downstream pathways regulated by this protein in beta cells. Nova1 KD altered the splicing of nearly 5000 transcripts. Pathway analysis indicated that these genes are involved in exocytosis, apoptosis, insulin receptor signaling, splicing and transcription. In line with these findings, Nova1 silencing inhibited insulin secretion and induced apoptosis basally and after cytokine treatment in rodent and human beta cells. These observations identify a novel layer of regulation of beta cell function, namely AS controlled by key splicing regulators such as Nova1.

Cytokines induce endoplasmic reticulum stress in human, rat and mouse beta cells via different mechanisms.

AIMS/HYPOTHESIS: Proinflammatory cytokines contribute to beta cell damage in type 1 diabetes in part through activation of endoplasmic reticulum (ER) stress. In rat beta cells, cytokine-induced ER stress involves NO production and consequent inhibition of the ER Ca(2+) transporting ATPase sarco/endoplasmic reticulum Ca(2+) pump 2 (SERCA2B). However, the mechanisms by which cytokines induce ER stress and apoptosis in mouse and human pancreatic beta cells remain unclear. The purpose of this study is to elucidate the role of ER stress on cytokine-induced beta cell apoptosis in these three species and thus solve ongoing controversies in the field. METHODS: Rat and mouse insulin-producing cells, human pancreatic islets and human EndoC-ßH1 cells were exposed to the cytokines IL-1ß, TNF-α and IFN-γ, with or without NO inhibition. A global comparison of cytokine-modulated gene expression in human, mouse and rat beta cells was also performed. The chemical chaperone tauroursodeoxycholic acid (TUDCA) and suppression of C/EBP homologous protein (CHOP) were used to assess the role of ER stress in cytokine-induced apoptosis of human beta cells. RESULTS: NO plays a key role in cytokine-induced ER stress in rat islets, but not in mouse or human islets. Bioinformatics analysis indicated greater similarity between human and mouse than between human and rat global gene expression after cytokine exposure. The chemical chaperone TUDCA and suppression of CHOP or c-Jun N-terminal kinase (JNK) protected human beta cells against cytokine-induced apoptosis. CONCLUSIONS/INTERPRETATION: These observations clarify previous results that were discrepant owing to the use of islets from different species, and confirm that cytokine-induced ER stress contributes to human beta cell death, at least in part via JNK activation.

IL-17A increases the expression of proinflammatory chemokines in human pancreatic islets.

AIMS/HYPOTHESIS: Cytotoxic T cells and macrophages contribute to beta cell destruction in type 1 diabetes at least in part through the production of cytokines such as IL-1ß, IFN-γ and TNF-α. We have recently shown the IL-17 pathway to be activated in circulating T cells and pancreatic islets of type 1 diabetes patients. Here, we studied whether IL-17A upregulates the production of chemokines by human pancreatic islets, thus contributing to the build-up of insulitis. METHODS: Human islets (from 18 donors), INS-1E cells and islets from wild-type and Stat1 knockout mice were studied. Dispersed islet cells were left untreated, or were treated with IL-17A alone or together with IL-1ß+IFN-γ or TNF-α+IFN-γ. RNA interference was used to knock down signal transducer and activator of transcription 1 (STAT1). Chemokine expression was assessed by quantitative RT-PCR, ELISA and histology. Cell viability was evaluated with nuclear dyes. RESULTS: IL-17A augmented IL-1ß+IFN-γ- and TNF-α+IFN-γ-induced chemokine mRNA and protein expression, and apoptosis in human islets. Beta cells were at least in part the source of chemokine production. Knockdown of STAT1 in human islets prevented cytokine- or IL-17A+cytokine-induced apoptosis and the expression of particular chemokines, e.g. chemokine (C-X-C motif) ligands 9 and 10. Similar observations were made in islets isolated from Stat1 knockout mice. CONCLUSIONS/INTERPRETATION: Our findings indicate that IL-17A exacerbates proinflammatory chemokine expression and secretion by human islets exposed to cytokines. This suggests that IL-17A contributes to the pathogenesis of type 1 diabetes by two mechanisms, namely the exacerbation of beta cell apoptosis and increased local production of chemokines, thus potentially aggravating insulitis.

A novel inhibitor of inducible NOS dimerization protects against cytokine-induced rat beta cell dysfunction.

BACKGROUND AND PURPOSE: Beta cell apoptosis is a major feature of type 1 diabetes, and pro-inflammatory cytokines are key drivers of the deterioration of beta cell mass through induction of apoptosis. Mitochondrial stress plays a critical role in mediating apoptosis by releasing cytochrome C into the cytoplasm, directly activating caspase-9 and its downstream signalling cascade. We aimed to identify new compounds that protect beta cells from cytokine-induced activation of the intrinsic (mitochondrial) pathway of apoptosis. EXPERIMENTAL APPROACH: Diabetogenic media, composed of IL-1ß, IFN-γ and high glucose, were used to induce mitochondrial stress in rat insulin-producing INS1E cells, and a high-content image-based screen of small molecule modulators of Casp9 pathway was performed. KEY RESULTS: A novel small molecule, ATV399, was identified from a high-content image-based screen for compounds that inhibit cleaved caspase-9 activation and subsequent beta cell apoptosis induced by a combination of IL-1ß, IFN-γ and high glucose, which together mimic the pathogenic diabetic milieu. Through medicinal chemistry optimization, potency was markedly improved (6-30 fold), with reduced inhibitory effects on CYP3A4. Improved analogues, such as CAT639, improved beta cell viability and insulin secretion in cytokine-treated rat insulin-producing INS1E cells and primary dispersed islet cells. Mechanistically, CAT639 reduced the production of NO by allosterically inhibiting dimerization of inducible NOS (iNOS) without affecting its mRNA levels. CONCLUSION AND IMPLICATIONS: Taken together, these studies demonstrate a successful phenotypic screening campaign resulting in identification of an inhibitor of iNOS dimerization that protects beta cell viability and function through modulation of mitochondrial stress induced by cytokines.

Tolerogenic insulin peptide therapy precipitates type 1 diabetes.

Daniel et al. (https://doi.org/10.1084/jem.20110574) have previously published in JEM a study on the preventive effect of tolerogenic vaccination with a strong agonist insulin mimetope in type 1 diabetes. Our study now challenges these results and shows that osmotic pump delivery of the modified insulin peptide R22E did not prevent hyperglycemia, accelerated disease onset, increased its incidence, and worsened insulitis.

Protective Role of Complement C3 Against Cytokine-Mediated ß-Cell Apoptosis.

Type 1 diabetes is a chronic autoimmune disease characterized by pancreatic islet inflammation and ß-cell destruction by proinflammatory cytokines and other mediators. Based on RNA sequencing and protein-protein interaction analyses of human islets exposed to proinflammatory cytokines, we identified complement C3 as a hub for some of the effects of cytokines. The proinflammatory cytokines interleukin-1ß plus interferon-γ increase C3 expression in rodent and human pancreatic ß-cells, and C3 is detected by histology in and around the islets of diabetic patients. Surprisingly, C3 silencing exacerbates apoptosis under both basal condition and following exposure to cytokines, and it increases chemokine expression upon cytokine treatment. C3 exerts its prosurvival effects via AKT activation and c-Jun N-terminal kinase inhibition. Exogenously added C3 also protects against cytokine-induced ß-cell death and partially rescues the deleterious effects of inhibition of endogenous C3. These data suggest that locally produced C3 is an important prosurvival mechanism in pancreatic ß-cells under a proinflammatory assault.

Differential cell autonomous responses determine the outcome of coxsackievirus infections in murine pancreatic α and ß cells.

Type 1 diabetes (T1D) is an autoimmune disease caused by loss of pancreatic ß cells via apoptosis while neighboring α cells are preserved. Viral infections by coxsackieviruses (CVB) may contribute to trigger autoimmunity in T1D. Cellular permissiveness to viral infection is modulated by innate antiviral responses, which vary among different cell types. We presently describe that global gene expression is similar in cytokine-treated and virus-infected human islet cells, with up-regulation of gene networks involved in cell autonomous immune responses. Comparison between the responses of rat pancreatic α and ß cells to infection by CVB5 and 4 indicate that α cells trigger a more efficient antiviral response than ß cells, including higher basal and induced expression of STAT1-regulated genes, and are thus better able to clear viral infections than ß cells. These differences may explain why pancreatic ß cells, but not α cells, are targeted by an autoimmune response during T1D.

Pancreatic α Cells are Resistant to Metabolic Stress-induced Apoptosis in Type 2 Diabetes.

Pancreatic α cells are exposed to metabolic stress during the evolution of type 2 diabetes (T2D), but it remains unclear whether this affects their survival. We used electron microscopy to search for markers of apoptosis and endoplasmic reticulum (ER) stress in α and ß cells in islets from T2D or non-diabetic individuals. There was a significant increase in apoptotic ß cells (from 0.4% in control to 6.0% in T2D), but no α cell apoptosis. We observed, however, similar ER stress in α and ß cells from T2D patients. Human islets or fluorescence-activated cell sorting (FACS)-purified rat ß and α cells exposed in vitro to the saturated free fatty acid palmitate showed a similar response as the T2D islets, i.e. both cell types showed signs of ER stress but only ß cells progressed to apoptosis. Mechanistic experiments indicate that this α cell resistance to palmitate-induced apoptosis is explained, at least in part, by abundant expression of the anti-apoptotic protein Bcl2l1 (also known as Bcl-xL).

TYK2, a Candidate Gene for Type 1 Diabetes, Modulates Apoptosis and the Innate Immune Response in Human Pancreatic ß-Cells.

Pancreatic ß-cells are destroyed by an autoimmune attack in type 1 diabetes. Linkage and genome-wide association studies point to >50 loci that are associated with the disease in the human genome. Pathway analysis of candidate genes expressed in human islets identified a central role for interferon (IFN)-regulated pathways and tyrosine kinase 2 (TYK2). Polymorphisms in the TYK2 gene predicted to decrease function are associated with a decreased risk of developing type 1 diabetes. We presently evaluated whether TYK2 plays a role in human pancreatic ß-cell apoptosis and production of proinflammatory mediators. TYK2-silenced human ß-cells exposed to polyinosinic-polycitidilic acid (PIC) (a mimick of double-stranded RNA produced during viral infection) showed less type I IFN pathway activation and lower production of IFNα and CXCL10. These cells also had decreased expression of major histocompatibility complex (MHC) class I proteins, a hallmark of early ß-cell inflammation in type 1 diabetes. Importantly, TYK2 inhibition prevented PIC-induced ß-cell apoptosis via the mitochondrial pathway of cell death. The present findings suggest that TYK2 regulates apoptotic and proinflammatory pathways in pancreatic ß-cells via modulation of IFNα signaling, subsequent increase in MHC class I protein, and modulation of chemokines such as CXCL10 that are important for recruitment of T cells to the islets.

Reversal of autoimmune diabetes by restoration of antigen-specific tolerance using genetically modified Lactococcus lactis in mice.

Current interventions for arresting autoimmune diabetes have yet to strike the balance between sufficient efficacy, minimal side effects, and lack of generalized immunosuppression. Introduction of antigen via the gut represents an appealing method for induction of antigen-specific tolerance. Here, we developed a strategy for tolerance restoration using mucosal delivery in mice of biologically contained Lactococcus lactis genetically modified to secrete the whole proinsulin autoantigen along with the immunomodulatory cytokine IL-10. We show that combination therapy with low-dose systemic anti-CD3 stably reverted diabetes in NOD mice and increased frequencies of local Tregs, which not only accumulated in the pancreatic islets, but also suppressed immune response in an autoantigen-specific way. Cured mice remained responsive to disease-unrelated antigens, which argues against excessive immunosuppression. Application of this therapeutic tool achieved gut mucosal delivery of a diabetes-relevant autoantigen and a biologically active immunomodulatory cytokine, IL-10, and, when combined with a low dose of systemic anti-CD3, was well tolerated and induced autoantigen-specific long-term tolerance, allowing reversal of established autoimmune diabetes. Therefore, we believe this method could be an effective treatment strategy for type 1 diabetes in humans.